This invention relates to a point detection system for a railway switch machine and an associated method of point detection for a railway switch machine.
As is known in the art, a common method for switching a train from one railroad track to another is to install an electric motor driven switch machine next to the switching point of the track. Current versions of these switch machines are typically operated from a remote location, therefore it is essential that a remote operator be able to determine the position of the switch. In addition, because switch point closure is imperative to safe railroad train operation, Federal Railroad Administration (FRA) rules and regulations mandate not only that the position of the switch points be mechanically locked to prevent the points from opening during train traffic but also that the locked position of the switch points be continuously monitored to detect any undesirable movement.
Prior art switch machines relied on mechanical devices to perform the point and lock detections. However, such mechanical arrangements were subject to degradation over time as a result of wear. In addition, other factors, such as weather, directly affected the reliability of such systems.
U.S. Pat. No. 5,806,809 discloses a railroad switch point position detecting system employing a plurality of proximity detectors positioned proximate to the switch point or points of a railroad switch. These proximity detectors for detecting switch point position are physically located on the switch points or corresponding stock rail. While the use of proximity detectors in general are an improvement over the previous mechanical systems, there are still noted shortcomings of the use thereof. For example, the proximity sensors employed by the ""809 patent provides no means to distinguish ON from shorted and OFF from open. Therefore, in a static situation, an ON sensor that shorts will go undetected. If the switch points were subsequently forced open, as would occur with a train running through in the wrong direction, it would go undetected. With the switch points forced open and not reflected in the indication circuit, a safety hazard is created.
There remains a need, therefore, for a point detection system for a railway switch machine that overcomes the disadvantages and shortcomings of the prior art and provides a safe and reliable means for detecting point position.
The invention has met or exceeded the above-mentioned needs, as well as other needs. The invention includes a point detection system for a railway switch machine having a housing where the point detection system comprises a point detector bar positionable in a normal point position and a reverse point position, and point detecting means positioned within the housing for detecting when the point detector bar is in the normal point position and when the point detector bar is in the reverse point position. Preferably, the point detecting means comprises a first inductive proximity sensor and a second inductive proximity sensor.
In addition, the invention includes a point detection system for a railway switch machine having a housing defining a first sidewall and an opposing second sidewall, a point detector bar with a first and a second end positionable in normal point position and a reverse point position, a slide bar positionable in a normal locked position and a reverse locked position, and an indication system for indicating switching and locking data wherein the point detection system comprises a support sleeve affixed within the housing to the first sidewall and the opposing second sidewall for receiving and slidably supporting the first end of the point detector bar therewithin. The point detection system further comprises an orifice defined in the first sidewall of the housing through which the point detector bar is slidably retained by the first sidewall such that the first end of the point detector bar is slidably captivated within the support sleeve within the housing and the second end of the point detector bar is positioned outside of the housing. The point detection system also comprises a point detector target integrally engaged with the first end of the point detector bar within the housing and a point detecting means positioned within the housing and coupled to the indication system for detecting the point detector target when the point detector bar is positioned in the normal point position and the reverse point position. Furthermore, the point detecting means generates a normal point detection signal that is transmitted to the indication system when the point detecting means detects the point detector target with the point detector bar in the normal point position and the point detector means generates a reverse point detection signal that is transmitted to the indication system when the point detecting means detects the point detector target with the point detector bar in the reverse point position. Preferably, the point detecting means includes at least one inductive proximity sensor.
The invention also includes a method of point detection for a railway switch machine having a housing, a point detector bar positionable in a normal point position and a reverse point position, and a slide lock bar positionable in a normal locked position in a reverse locked position, wherein the method comprises the steps of: providing point detecting means in the housing adjacent to point detector bar; detecting with the point detecting means the position of the point detector bar; generating by the point detecting means a point detection signal representative of the position of the point detector bar; and delivering the point detection signal to means for processing and determining if said point detector bar is in the normal point position, the reverse point position, or in neither the normal point position nor the reverse point position. The method may also include the steps of employing as said point detecting means a first proximity sensor for detecting when the point detector bar is in the normal point position and a second proximity sensor for detecting when the point detector bar is in the reverse point position, and employing as said first proximity sensor and said second proximity sensor inductive proximity sensors.